1. Field of the Invention
The present invention relates to a hydraulic pressure reservoir having at least one pressure chamber with a fluid connection to a hydraulic circuit, and that is arranged between a movable partition positioned in a housing and a fixed partition, and that includes a pressure limiting valve.
2. Description of the Related Art
Hydraulic circuits are employed in many applications, for example to trigger control pulses or also to produce an actuating force by actuating a piston/cylinder unit.
An automatically operated clutch can be operated by means of a hydraulic actuator, for example, or such a hydraulic circuit can also be employed to adjust the transmission ratio between the two pairs of conical disks of a belt-driven conical-pulley transmission. When such an actuating force has to be built up very quickly, the start-up process of an electric motor of an electrically-powered hydraulic pump can result in the start-up time needed for the start-up process of the electric motor being too long. It is therefore necessary to hold a certain volume of pressure fluid in reserve at a predetermined pressure, so that the required actuating force can be built up in the required time with the pressure fluid.
Hydraulic pressure reservoirs in the form of a membrane reservoir, for example, can be employed to keep that volume of pressure fluid ready at the predetermined pressure level. The membrane reservoir, however, has the disadvantage that, on the one hand, the membrane is not completely pressure-tight, and, on the other hand, it is subject to fatigue effects, so that the life span required of the pressure reservoir cannot be met with the membrane reservoir.
A further possibility of such a pressure reservoir is a piston pressure tank with a helical spring, with which the desired quantity of pressure fluid can be stored at the predetermined pressure level. Such a piston pressure tank has a pressure piston that is axially movable in a cylinder, whereby the pressure fluid can be kept at the desired pressure level. However, as the pressure rises, the problems of the seal between the pressure piston and the cylinder wall also increase, so that it is necessary to produce the fit between the pressure piston and the cylinder with high precision, which results in high production costs. Furthermore, the piston pressure tanks require that tipping or tilting of the piston in the cylinder bore must be prevented, so that the piston must include a certain guide length in order to be able to seal well.
The same problem also arises with a piston pressure tank acting against gas pressure, where the helical spring has merely been replaced by a gas reservoir.
In that regard, an object of the present invention is to provide a hydraulic pressure reservoir that can be manufactured economically, that also eliminates the problem of the pressure chamber leaking, and, additionally, that has little wear after many load change cycles and thus is distinguished by a long life span.